A LOT of attention is given to the Louisiana Purchase but I have heard almost nothing about reaction to the land acquisition of northern Mexico apart from US and Mexican politicians.
Both states at the time were far, far removed from the geopolitically important important Great Powers of Europe. There wasn't too much of a reason for any of them to object -- America was across an ocean and the acquisition of more territory from another independent state wouldn't affect the geopolitical security of any of the European powers significantly. Lord Ashburton of the UK even stated that his government "did not have any objection to the United States making an acquisition of territory in that direction." (George Lockhard Rives, The United States and Mexico, 1821-1840, pp. 45-46).